Brazilian prison gangs have been in the news a lot lately. And that's largely because, in the first few days of January 2017, more than 100 prisoners were brutally murdered by fellow inmates in two separate incidents in the northern states of Amazonas and Roraima. Despite the recent attention that has been paid to them, however, Brazilian prison gangs are not new. The Comando Vermelho, for example, the country's oldest and perhaps most infamous prison gang, emerged from inside the walls of a state penitentiary on an island off the coast of Rio de Janeiro as far back as the mid-1970s and has been causing problems for the authorities ever since.

The most powerful prison gang in Brazil today, however, is the Primeiro Comando da Capital, or PCC, which is historically based in São Paulo but is now thought to operate throughout...